The Turbine Hall at the Tate Modern. A glorious adaptive reuse, and one that created one of the most iconic spaces in the museum world, that of the old Turbine Hall. Rather than fill the great void with new floors or ring the walls with art, it was left as an impressive canvas, a shell that itself is grand and uplifting and inspires wonder while forming the basis for temporary and site-specific installations, artwork of a place, all capped by a new, glowing, roof lantern. One room, many faces.
Speaks for itself. Very cool.